A small-size electronic device that stores and processes input information can temporarily store input information in an internal storage medium, and then process data in a prescribed manner. These kinds of electronic devices are for example preferably applied to a music data delivery system and the like. They include such terminal devices as personal computers, home game machines, and mobile phones. In information delivery systems for these kinds of electronic devices, a technique of web cache is utilized to make it easier to deliver desired information. In the process of web cache, data of searched web pages are stored in a certain memory on a client terminal side for future use, which is to say the data stored are utilized to display the web pages next time they are requested.
In general, World Wide Web (WWW) browsers such as Internet Explore are equipped with a function that can display and browse pages in response to user operation. The WWW browser can perform the process of web cache to display web pages. To improve its response time, the WWW browser cashes pages before a user moves to this layer. The WWW browser also cashes the pages browsed. This eliminates unnecessary network access when the user returns to the previous layers. For example, the WWW browser can cache page information of a certain URL with its last access date and time. The WWW browser can cache pages on different layers.
There has been proposed information processing apparatus that searches through the Internet for web pages provided by WWW services of video cameras and displays them on a display section for example (Patent Document 1). This allows even a small-size electric device to implement the web cache, by storing data of searched web pages in an external storage medium. When the same web pages are requested, the device can quickly display them, because this device does not search for them again through the Internet. The device reads out their data from the storage medium, and then displays the web pages based on them.
That is to say, those kinds of electronic devices do not download the page information (content) through the Internet when a user specifies the same URL. The devices read out them from cache memories of the client terminal (video cameras). In this case, both to improve the efficiency of usage of the cache memories and to store new data in them at any time, the device removes data with the oldest last-access time from them due to the limitation of its capacity.    Patent Document 1: Japanese Patent Publication No. 2003-122620 (Paragraph Number [0010] through [0018], and FIG. 1)
However, according to the conventional method of web cache, the WWW browser, such as Internet Explore, caches web pages in a page unit. The terminal device with a small-capacity memory, such as mobile phones, cannot repeatedly read out the content (image data, sound information and the like) even if this content is included in a plurality of pages. This would be an inefficient use of the memory.
Also, the web pages that users often visit include a large amount of content data such as sound data and image data, and many are rarely updated on the Web for example. Particularly, it takes time to download data of portal web pages through a network, when these content data are not cached in the terminal device.
In addition, the format of cache data is defined on the Web. The terminal device needs time to convert the format each time it uses the data. Therefore, even if the terminal device utilizes the data stored in the cache, it needs time to process them.